Hope you are all enjoying the summer so far and keeping busy. Although, we’re about 2 months away from the Fall produce season, it’s never too early to begin thinking of IPM strategies you will be using to battle key insects next season. This includes keeping track of their typical activity during June, July, and August. Below is a short discussion detailing individual pests. 
 
Aphids:    The major aphid species that are important in produce crops each spring include green peach aphid, foxglove aphid and lettuce aphid.  These species are considered cool season pests and are biologically most active during the winter and spring when temperature average around (55-65 F). We do not find them on summer crops as the high temperatures prohibit their activity. They essentially become extinct each summer only to reappear in the fall to infest crops in Oct-Dec migrating into the desert via N-NW winds that occur after the monsoons.
 
Diamondback Moth (DBM):  Another key pest that disappears each summer but for a different reason than for aphids. The host range of DBM is limited to only brassica crop and plants. Although brassica weeds are common during the winter, they occur during the summer due to high temperatures and dry conditions. Thus, like aphids, DBM populations from the previous spring season become “extinct” during the summer when brassica crops and weeds are absent. They reappear each fall migrating in on high winds associated with tropical storms from Mexico, or arrive into the region on infested brassica transplants from California.
 
Whiteflies:       A resident pest that occurs year-round in the desert. As a warm season pest, whiteflies are most abundant on fall produce crops, and seldom a problem during the winter and spring. Peak abundance occurs during the summer months on cotton, and again in September and October on fall brassica, leafy vegetables and fall melons.  Thus, it is important to control whiteflies in cotton prior to defoliation to prevent large migrations onto fall produce crops. In addition, whiteflies can be found on several weeds such as purslane, goosefoot, ground cherry, and sunflowers. Sanitation in and around fields being prepped for fall plantings is important. Preventatively, growers should consider applying soil, system insecticides such as imidacloprid or Verimark to Fall produce crops.

Beet Armyworm (BAW):  A warm-season pest that occurs year-round in the desert. They tend to reach peak abundance twice a year. Generally, the most important peak is in September and October when weather is ideal for their development, flight activity and oviposition. A second peak occurs in late spring. Activity is generally light during the summer, occurring primarily in alfalfa crops. Although BAW is known to migrate in from the south via monsoon and tropical storms, resident populations annually occur in alfalfa during the summer. Thus, to minimize BAW in fall produce crops, thorough management of BAW can potentially minimize their movement onto Fall produce crops.  Weeds are also a source of BAW (purslane, goosefoot, sunflower and Russian thistle) so sanitation in and around fields is important.
 
Western Flower Thrips (WFT):  Also a resident pest that can be found in the desert year round. WFT is most abundant on lettuce in the late spring, but peaks in abundance on alfalfa, melons and cotton is May and June. During the late summer numbers drop dramatically where thrips can be found on melons and alfalfa and weeds like goosefoot and purslane. WFT slowly move into lettuce again in early fall and are least abundant during the winter.  Sanitation of weeds during the summer can help reduce thrips abundance moving into the fall crops and weeds.
 
For more information see:   Keeping Track of Major Produce Pests During the Summer

In the past year we have experienced huge fluctuations in the global fertilizer markets.  In 2022, fertilizer shortages developed and the price of fertilizers increased up to 180% in some cases.  

 
These large fluctuations have been largely due to changes in trade flows with Russia because of the tensions in the region, sanctions imposed on Russia, inflation, and other pandemic-related complications with transportation logistics.  Collectively, expensive fertilizer prices have been a challenge globally and certainly in our crop production systems of the desert Southwest.
 
Recently, several retail fertilizers have varied significantly in the market trends.  For example, in May 2023 about half of the major retail fertilizers are higher compared to April prices and the other half has lower prices than last month (Quinn, 2023).
 
Urea (46-0-0) has gone up 6% in retail markets since last month with an average price of $664/ton.  A few weeks ago, urea was below $600/ton for the first time since late 2021.  Similarly, diammonium phosphate (18-46-0), monoammonium phosphate (11-52-0), and urea ammonium nitrate (32-0-0) had an average the past month of $517/ton.
 
In contrast, anhydrous ammonia (82-0-0) has had an average price recently of $910/ton, which is down about 9% in price from April 2023.  Several other major fertilizers have been lower in price the past month.  Muriate of potash (KCl, 0-0-60) had an average price in the past month of $627/ton, ammonium polyphosphate (10-34-0) average price has been $739/ton, and urea ammonium nitrate (UAN-32, 32-0-0) average price has been $423/ton this month.
 
Note that several of the major fertilizer materials come in different forms.  For example, urea ammonium nitrate (UAN) is 28% N in some materials and 32% N in another common form.  Also, monoammonium phosphate (MAP) can have N concentrations of 10-12% and P₂O₅ concentrations of 48-61% with 11-52-0 being probably the most common form in the market.
 
Considering the overall trends in the past few years, international fertilizer prices have been generally decreasing since the summer of 2022.  Today, international fertilizer prices are back in a range close to early 2021.  International fertilizer prices are not expected to drop below pre-pandemic levels, primarily due to global inflation that generates an increase in production and transportation costs (Figure 1).
 
Several expert sources in the fertilizer industry are projecting a drop in international fertilizer prices in the coming months by approximately 50% of the prices experienced last year.   Accordingly, many fertilizer importers are waiting to ship to markets and farmers are often waiting and watching for the projected drop in fertilizer prices to materialize before purchasing (Schnitkey et al., 2023).
 
Despite the high degree of volatility in international fertilizer markets and the limited availability of fertilizers in some crop production sectors that have recently been experienced, it is expected that the downward trends will continue.
 
Looking ahead, many experts in the international fertilizer industry are recommending for producers to not wait until too late to purchase fertilizers for upcoming crops, utilize economies of scale when purchasing fertilizers materials as much as possible, and of course watch the trends in fertilizer markets.  International logistics in the fertilizer industry, including shipping, transfer, and distribution of fertilizer cargo is proving to be very important in realizing a more stable fertilizer market for the future.

Figure 1.  Example of fluctuations in fertilizer prices per ton of material from
January 2021 through March 2023.  Source:  Schnitkey et al. 2023

References:
Schnitkey, G., N. Paulson, C. Zulauf and J. Baltz. 2023. Fertilizer Prices and Company Profits Going into Spring 2023. farmdoc daily (13):36, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, 28 February 2023.
 
Quinn, R. 2023.  DTN Retail Fertilizer Trends: Fertilizer prices moving in two directions. DTN Newsletter, 17 May 2023. https://www.dtnpf.com/agriculture/web/ag/crops/article/2023/05/17/fertilizers-moving-two-directions

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches between bed centers. All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart. 

Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.  

Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves  ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any treatments in this trial.

ANR Webinar 10/17 click link for details.

 Fig. 1. Finger weeders removing a large, in-row Palmer Amaranth plant in cotton – slow motion video. (Video credit: Kyle R. Russel, Texas A&M University. Cultivator design and setup credit: Carl Pepper, Lubbock, TX). Click here or on the image to see the video. 

Surveying the Yuma area, we have observed a lot of Hairy Fleabane (Conyza bonariensis) and received calls from PCA's regarding this weed and its control. 
We have observed that the application of Glyphosate is not showing good efficacy in controlling this species in parts of Yuma and Phoenix area. 
Resistance to glyphosate has been reported in some grain growing areas of Queensland and northern New South Wales and other cropping regions across Australia ⁽¹⁾ as well as Spain ⁽²⁾.
Other cases of resistance to other herbicides such as paraquat, and 2,4-D have been confirmed ⁽³⁾.
In the International Herbicide Resistance Weed Database it is reported that in Switzerland that both Conyza canadiensis (Horseweed) and Conyza bonariensis (Hairy Fleabane) presented resistance to a HRAC Group 9 herbicide last year. We found resistance reported in California only and not in Arizona ⁽⁴⁾.

Some of our PCA amigos and field technicians have reported having problems finding a good treatment for fleabane due to possible glyphosate resistance. We included Glufosinate and Embed Extra in a trial last year. The images below show good results of an application of Rely at a high rate (82floz) with two applications at a 2-week interval. The second picture shows the efficacy of Embed Extra (2 pt.) following the same application schedule. Weeds were ~2-3” at the time of application. Some growers have reported good results with glufosinate in Waddell AZ. Sharpen has also been used by Yuma citrus growers.  
A study showed that plants grown at 90% relative humidity presented more translocation of glufosinate than those grown at 35%. Relative humidity had greater effect than temperature on glufosinate toxicity to Palmer amaranth, redroot pigweed, and common waterhemp ⁽⁵⁾. In a trial conducted by Barry Tickes from UA nutsedge control was better in an August application with a ~40% RH than a June application with ~20% RH.
As always please check labels and registration before using these treatments.

Figure 1. Hairy fleabane control with Glufosinate


Figure 2. Hairy Fleabane control with Embed Extra

References:

1. https://bnrc.springeropen.com/articles/10.1186/s42269-020-00316-w

2. https://cdnsciencepub.com/doi/10.1139/cjps-2018-0254

3. https://bioone.org/journals/weed-technology/volume-35/issue-4/wet.2021.11/Cross-resistance-to-diquat-in-glyphosate-paraquat-resistant-hairy-fleabane/10.1017/wet.2021.11.short

4. https://www.weedscience.org/Pages/Species.aspx

5. Coetzer, E., Al-Khatib, K., & Loughin, T. (2001). Glufosinate efficacy, absorption, and translocation in amaranth as affected by relative humidity and temperature. Weed Science, 49(1), 8-13. doi:10.1614/0043-1745(2001)049[0008:GEAATI]2.0.CO;2

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased considerably y in the past 2 weeks and about average for late summer
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Wellton) particularly near alfalfa
 
Cabbage looper:         
Cabbage looper numbers remain low consistent previous years.
 
Diamondback moth:      
DBM moths were not caught in any trap since June; average for this time of the year.
 
Whitefly:                      
Adult movement decreased in past 2 weeks consistent with previous years
 
Thrips:                         
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity has highest in Wellton and Dome Valley, and slightly above average for early August